[CEDET-devel] parsers' plug-in API

[<pon...@ne...>]

Hi Eric,

I finally got time to work on an uniform way to plug the different
parsers into Semantic :-)

Attached you will find a tarball of all the files I updated (mainly in
wisent stuff) to achieve that.  Just notice that this work, even if
all seems to work well, is probably alpha-release quality and needs
more testing ;-)

The tarball contains a ChangeLog.  Here is an overview of new design.

After studying the code in semantic.el I observed that the only
function which is actually specific to the parser is
`semantic-bovinate-nonterminal'.  All other parser related functions
rely on it!

So I concluded that the more natural way to plug new parsers in
Semantic would be to allow overriding of that function!

IMO, this design has several advantages:

- It is very simple, only one function need to be overrode.

- It permits to reuse most of the existing parsing code.

- Semantic's behavior is consistent, as it not depends on the parser
  actually used.

The main requirement with a such design is that the new parser must be
able to parse one nonterminal at a time!  Because
`semantic-bovinate-nonterminal' must return one raw semantic token at
each call.  Fortunately the current LL and LALR parsers can do that
:-)

In the attached first implementation, I made the following changes in
semantic.el:

- Removed all references to the default nonterminal symbol
  'bovine-toplevel which is specific to the LL parser.  Now the
  default nonterminal is nil!  These references were unnecessary
  because `semantic-bovinate-nonterminal' already used
  'bovine-toplevel as the default nonterminal value.

- Created a new buffer-local variable `semantic-bovinate-parser' that
  specifies the override function for `semantic-bovinate-nonterminal'.

- Renamed `semantic-bovinate-nonterminal' to
  `semantic-bovinate-nonterminal-default'.

- Implemented `semantic-bovinate-nonterminal' as a wrapper to call
  the function specified in `semantic-bovinate-parser', or to call
  `semantic-bovinate-nonterminal-default' by default.

- Fixed a little problem in `semantic-bovinate-nonterminals' that
  didn't correctly setup the 'reparse-symbol property of expanded
  tokens.

The rest of my work consisted in updating Wisent's stuff to obey the
new API!  As you will notice I removed a lot of code no more
necessary, from wisent-bovine.el ;-)

Unfortunately the new design has broken the wisent-java.wy/el
implementation which was designed to parse a Java source in one pass
like traditional bison use _ that is the grammar returns a list of
tokens ready for use instead of one raw token as required by the
`semantic-bovinate-nonterminal' API :-(

IMO, this is not really a big issue.  It is far better to use the
"semantic orthodox" implementation in wisent-java-tags.wy/el!

I am looking forward for you remarks ;-)

Thank you for your time!
David



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